Vagiallene, a Rearranged C15Acetogenin from Laurencia obtusa

Vagiallene (1), a rearranged C15acetogenin with a molecular formula and a carbon skeleton unprecedented in natural products, was isolated as a trace constituent from the organic extract of the red alga Laurencia obtusafrom Lefkada island. The planar structure and the relative configuration of 1were established on the basis of extensive analysis of its spectroscopic data, while its absolute configuration was determined by comparison of its experimental and quantum-mechanically predicted electronic circular dichroism spectra.